This invention relates to computer,controlled graphical drawing and editing systems and methods, and in particular to such drawing and editing systems based on object-oriented display representations.
Graphical drawing and editing systems are generally of two kinds: painting programs and structured drawing programs. Painting programs allow the user to paint lines (or "spray" patterns) and erase on an image-based representation, usually a two-dimensional array of pixels. Structured drawing programs allow the user to create, modify, and delete geometrically-defined objects. An object-based representation, as distinguished from an image representation, has many advantages for computation, but the user interface to such a representation has typically used more discrete actions, which are more awkward for the user. Especially for computer systems with pen (or stylus) input devices for various size displays, from notebook-sized to whiteboard-sized displays, the problem has been troublesome. While many drawing systems allow drawing and, for example, erasing of images with pen-based motions, it is accomplished on a pixel by pixel basis of the pixel-array image representation. Where object-based representations are used, erasing has been done by discrete actions, such as drawing a loop around some objects and then evoking a delete operation.
The problem is much worse for large scale interactive displays for supporting group meetings and presentations. An example is the Liveboard, described in a paper to be published in Proceedings of CHI,92, the ACM Conference on Human Factors in Computing Systems, May 3-7, 1992 Monterey, Calif. The latter employs a bitmap painting program which requires pixel-map based representations for the display. This is very limiting with respect to the flexibility in dealing with objects.